Mineralium Deposita最新文献

{"title":"A newly recognised mafic sill-hosted Ni-sulfide deposit emplaced during the 2.4 Ga Widgiemooltha dike swarm event, Eastern Goldfields, Western Australia","authors":"Coralie Siégel, Louise Schoneveld, Catherine Spaggiari, Margaux Le Vaillant, Stephen Barnes, Belinda Godel, David Mahon, Michael Verrall, Laure Martin, Stefano Caruso, Tina Shelton","doi":"10.1007/s00126-024-01305-z","DOIUrl":"https://doi.org/10.1007/s00126-024-01305-z","url":null,"abstract":"<p>The Cathedrals Ni-Cu prospect, located at the western margin of the Eastern Goldfields of the Yilgarn Craton, is hosted within a mafic intrusion interpreted as a sill complex. U-Pb dating of apatite from the sill yielded a crystallisation age of 2336 ± 64 Ma, inferring an association of sill emplacement and Ni mineralisation related to emplacement of the c. 2400 Ma Widgiemooltha dike swarm. The sill is typically differentiated into a lower olivine orthocumulate layer overlain by a dolerite unit containing xenoliths of partially assimilated granitoids in its upper portion. The latter is interpreted to be the result of stoping and melting of the granitic hanging wall, thereby creating a gravitationally stable buoyant melt layer beneath the top contact. Ni-Cu-Fe sulfides are increasingly abundant towards the base of the sill, ranging from globular disseminated sulfides to net-textured and massive sulfides at the basal contact. The presence and orientation of sulfide globule-bubble pairs indicates a primary near-horizontal orientation. Massive sulfides commonly exhibit a loop texture with pyrrhotite grains surrounded by pentlandite and chalcopyrite. Despite the variety of sulfide textures, sulfur isotopes have a homogeneous mantle-like signature without significant mass independent fractionation. Mineral chemistries that indicate sulfide prospectivity in larger intrusions do not work as effectively in this small sill, therefore new indicators may need to be developed to explore for similar deposits. To date, there are no other known magmatic deposits of this age in Australia. Sills of this age may be more prospective than previously recognised.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"17 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142013741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogy, mineral chemistry, and genesis of Cu-Ni-As-rich ores at Lisheen, Ireland","authors":"Max Frenzel, Markus Röhner, Nigel J. Cook, Sarah Gilbert, Cristiana L. Ciobanu, John F. Güven","doi":"10.1007/s00126-024-01299-8","DOIUrl":"https://doi.org/10.1007/s00126-024-01299-8","url":null,"abstract":"<p>The Irish Orefield is characterised by the presence of both Zn-Pb- and Cu-Ni-As-rich deposits, prospects, and orebodies in similar structural and stratigraphic positions. However, the genetic relationships between these mineralisation types are still debated. In this article, we present new mineralogical, paragenetic, and mineral-chemical observations from the Cu-Ni-As-rich ores at the classic Lisheen deposit, County Tipperary. These observations indicate the intimate association and cogenetic nature of these ores with the more abundant Zn-Pb-rich mineralisation. Specifically, both mineralisation types appear to have formed at the same time, under similar physicochemical conditions, and from the same ore fluids. In addition, both types of mineralisation contain elevated Ge contents. The cogenetic nature of the two mineralisation types, the relative absence of Cu-Ni-As-rich ores from most of the larger Irish-type Zn-Pb deposits compared to expectations derived from probable ore fluid compositions, and finally, the known geological characteristics of larger Cu-Ni-As-rich ore bodies, like Gortdrum, indicate that significant Cu-Ni-As-rich mineralisation could be present at lower stratigraphic levels across the Irish Orefield. Areas with extensive known Zn-Pb mineralisation are expected to be particularly prospective for such ores, which may occur at stratigraphic levels as deep as the Old Red Sandstone. This may have additional implications beyond Ireland, and could point to the potential for undiscovered Cu-rich ores in low-temperature carbonate-hosted Zn-Pb districts elsewhere.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"14 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141986599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineral chemistry of the Geyer SW tin skarn deposit: understanding variable fluid/rock ratios and metal fluxes","authors":"Nicolas Meyer, Mathias Burisch, Jens Gutzmer, Joachim Krause, Henning Scheibert, Gregor Markl","doi":"10.1007/s00126-024-01297-w","DOIUrl":"https://doi.org/10.1007/s00126-024-01297-w","url":null,"abstract":"<p>The Geyer tin skarn in the Erzgebirge, Germany, comprises an early skarnoid stage (stage I, ~ 320 Ma) and a younger metasomatic stage (stage II, ~ 305 Ma), but yet, the source and distribution of Sn and the physicochemical conditions of skarn alteration were not constrained. Our results illustrate that contact metamorphic skarnoids of stage I contain only little Sn. REE patterns and elevated concentrations of HFSE indicate that garnet, titanite and vesuvianite of stage I formed under rock-buffered conditions (low fluid/rock ratios). Prograde assemblages of stage II, in contrast, contain two generations of stanniferous garnet, titanite-malayaite and vesuvianite. Oscillation between rock-buffered and fluid-buffered conditions are marked by variable concentrations of HFSE, W, In, and Sn in metasomatic garnet. Trace and REE element signatures of minerals formed under high fluid/rock ratios appear to mimic the signature of the magmatic-hydrothermal fluid which gave rise to metasomatic skarn alteration. Concomitantly with lower fluid-rock ratio, tin was remobilized from Sn-rich silicates and re-precipitated as malayaite. Ingress of meteoric water and decreasing temperatures towards the end of stage II led to the formation of cassiterite, low-Sn amphibole, chlorite, and sulfide minerals. Minor and trace element compositions of cassiterite do not show much variation, even if host rock and gangue minerals vary significantly, suggesting a predominance of a magmatic-hydrothermal fluid and high fluid/rock ratios. The mineral chemistry of major skarn-forming minerals, hence, records the change in the fluid/rock ratio, and the arrival, distribution, and remobilization of tin by magmatic fluids in polyphase tin skarn systems.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"2 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of the 1149 Ma Etoile Suite Mafic Intrusion, Quebec: implications for vanadium mineralisation in Proterozoic anorthosite-bearing terranes","authors":"Randolph P. Maier, Sarah A. S. Dare, William D. Smith","doi":"10.1007/s00126-024-01298-9","DOIUrl":"https://doi.org/10.1007/s00126-024-01298-9","url":null,"abstract":"<p>Iron-titanium-vanadium (Fe-Ti-V) oxide mineralisation is commonly associated with Proterozoic massif-type anorthosites, but the conditions required for their formation remain poorly understood. The Etoile Suite Mafic Intrusion (1149 ± 11 Ma), in the Grenville Province, Quebec (Canada), comprises a layered mafic intrusion that is coeval with nearby massif-type anorthosites. The mafic intrusion consists of troctolite and olivine gabbro cumulates, where magnetite and ilmenite are intercumulus at the base (Zone A) and top (Zone C) but cumulus (&lt;30 modal %) in the centre (Zone B). Towards the base of Zone B, vanadium mineralisation occurs in a 1-km-thick oxide-rich wehrlite horizon, where V-rich titanomagnetite (&lt;1.85 wt% V₂O₅) and ilmenite form semi-massive oxide layers. From the base to the top of Zone B there is an overall progressive decrease in An_pl, Fo_ol, and Mg#_cpx, and in Cr and Ni concentrations of magnetite, albeit with several reversals to more primitive compositions, including one near the base of Zone C. This indicates fractional crystallisation in an open magma chamber. The intrusion crystallised at moderate <i>f</i>O₂ (~FMQ 1.1 ± 0.3), resulting in the late crystallisation of V-rich magnetite from a relatively evolved magma. The parental magma was likely a high-Al basalt derived from a depleted mantle source, recording minimal crustal contamination, in contrast to coeval massif-type anorthosites that commonly contain orthopyroxene reflecting higher degrees of crustal contamination. As a result, V mineralisation in noritic anorthosites formed at higher <i>f</i>O₂, with early crystallisation of relatively V-poor magnetite, whereas magnetite in troctolitic-olivine gabbroic intrusions crystallised later with higher V contents, due to lower <i>f</i>O₂.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"13 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141910294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relationship between U and Ni-Co-As mineralization in the Midwest polymetallic U deposit, Athabasca Basin (Canada) – constraints from mineralogical, geochemical, and fluid inclusion studies","authors":"Daniel Ferguson, Guoxiang Chi, Charles Normand, Julien Mercadier, Yumeng Wang, Kelsey McKee, Magdalena Anderson, John Robbins","doi":"10.1007/s00126-024-01304-0","DOIUrl":"https://doi.org/10.1007/s00126-024-01304-0","url":null,"abstract":"<p>The unconformity-related uranium (URU) deposits in the Proterozoic Athabasca Basin are one of the most important U resources in the world. This type of U deposit can be divided into monometallic (U) and polymetallic (U-Ni-Co-As) subtypes. While it is generally agreed that the URU deposits formed from reaction between oxidizing, basinal brines carrying U and/or Ni-Co-As with reducing basement fluids or lithologies, it is debatable whether the polymetallic deposits formed from co-enrichment of U-Ni-Co-As or enrichment of U superimposed by a separate Ni-Co-As mineralization event. This study addresses this problem through mineralogical, geochemical and fluid inclusion investigation of the Midwest U-Ni-Co-As deposit. Petrographic studies indicate that the sequence of ore precipitation started with uraninite, followed by Ni-Co arsenides and sulfoarsenides and then Cu-Pb-Fe sulfides, and this sequence was repeated episodically. This observation suggests that the deposit did not form from two separate U and Ni-Co-As mineralization events, but rather multiple episodes of U-Ni-Co-As mineralization. Linear correlations between chemical ages and Si-Ca-Fe contents of the most pristine uraninite U1 suggest a maximum primary mineralization of ca. 1600 Ma, which is consistent with the inferred primary U mineralization age in the Athabasca Basin. Microthermometric and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in syn-mineralization drusy quartz indicate that the composition of the ore-forming fluids is characterized by the H₂O-NaCl-CaCl₂-KCl-MgCl₂ system and comparable to those from both monometallic and polymetallic URU deposits. The relationship between U and Ni + Co in the fluid inclusions and its comparison with other URU deposits support a model in which U and Ni-Co were co-enriched in a unified mineralization process. The development of breccia structures in the ores and the dramatic fluid pressure fluctuation revealed by fluid inclusions suggest that the deposit formed from multiple episodes of fluid flow related to repeated reactivation of basement-rooted faults.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"66 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141909081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Davenda-Klyuchevskoe Au-Mo-(Cu) cluster in the Mogocha gold district (Russia): an intrusion-related or porphyry system overprinted by epithermal gold?","authors":"Alexander Yakubchuk, Konstantin Lobanov, Sergei Shmatov","doi":"10.1007/s00126-024-01302-2","DOIUrl":"https://doi.org/10.1007/s00126-024-01302-2","url":null,"abstract":"<p>The 18 × 4 km Davenda-Klyuchevskoe cluster in the Mogocha mineral district of the Siberian craton hosts gold, silver, molybdenum and copper in six types of mineralization. The general sulphide zoning at the Sergeevskoe and Klyuchevskoe deposits, the largest in the cluster, is similar to porphyry systems, but the orebodies form 4.5 × 1 km multiple linear sulphide-rich quartz-veinlet swarms, rather than a bulk mineralized envelope. Five types of mineralization formed at 162 − 150 Ma. They are clearly overprinted by northeast-striking epithermal Au-Ag carbonate-quartz veins. All mineralization is genetically linked to the Peak Klyuchi subvolcanic centre of Late Jurassic to Early Cretaceous age (159 − 132 Ma) which is part of the Amudzhikan intrusive complex, consisting of early complexly shaped ENE-striking granodiorite porphyry stock and dykes, intruded by magmatic to hydrothermal breccia and five generations of WNW-trending dykes of dioritic porphyry, hybrid porphyry, rhyolite, and ultimate lamprophyre. The dykes control or parallel five types of megastockwork orebodies within a dextral extensional strike-slip duplex. However, Au-Ag epithermal veins follow late-mineral northeast faults, dividing the megastockwork into several domains. The Davenda-Klyuchevskoe cluster is part of the Shilka Mo-(Au-Ag-Cu) metallogenic belt, striking within the Siberian craton just 25 km north in parallel to the Mongol-Okhotsk suture. Geochronological and petrological data suggest that the intrusive complex and its mineralization formed in relation to northward-dipping subduction prior to scissor-like suturing in this segment of the Mongol-Okhotsk Ocean in response to the northward push by the North China and Yangtze cratons towards Siberia.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"190 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141899853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global constraints on exhumation rates during porphyry copper formation and supergene enrichment: applications to exploration as illustrated from the Central Andes","authors":"Laura Evenstar, Simon Dahlström, Adrian Hartley, T. Campbell McCuaig, Anne Mather, Joe Shaw","doi":"10.1007/s00126-024-01303-1","DOIUrl":"https://doi.org/10.1007/s00126-024-01303-1","url":null,"abstract":"<p>Currently, 60% of the world’s copper production comes from porphyry copper deposits, often significantly enriched by surface weathering. This paper uses new global datasets and previous work to review the critical processes required for porphyry copper formation and supergene enrichment. Porphyry copper formation requires a subducting arc to create a source magma which traverses a thickened crust subject to high exhumation rates during formation, ranging from 100’s to 1,000’s m/m.y. High exhumation rates potentially trigger magma decompression, causing fluid release, opening fluid pathways along faults and lineaments and/or facilitating telescoping, whereby early porphyry-style mineralization is overprinted and enriched by high-sulfidation mineralization at shallower crustal levels. Later supergene enrichment of the deposit requires precipitation rates &gt; 120 mm/yr and exhumation rates ranging from 10’s to 100’s m/m.y. This allows copper sulfide sources to be continually refreshed for weathering but restricts the amount of erosion. Using the Central Andes, one of the world’s most critical porphyry copper provinces, the understanding gained from analyzing these global databases can explain the temporal and spatial pattern of known deposits. These constraints were used to inform mappable target criteria and data required for mineral exploration at a range of different scales, from orogen (&gt; 100,000 km²), to terrane (100,000–1,000 km²) to arc (1,000–100 km²). The results can be used to help illustrate and inform global exploration strategies for supergene-enriched porphyry copper deposits.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"75 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revising PGE deposition and remobilization mechanisms using new data from the historic Vermilion and Crean Hill mines, Sudbury, Canada","authors":"Carol-Anne Généreux, Bruno Lafrance","doi":"10.1007/s00126-024-01301-3","DOIUrl":"https://doi.org/10.1007/s00126-024-01301-3","url":null,"abstract":"<p>Platinum-group element (PGE) mineralization associated with the Sudbury Igneous Complex (SIC), Canada, generally occurs within brecciated footwall rocks. At the Crean Hill and Vermilion deposits, variations in the ore mineralogy, textures, and whole rock geochemical signatures suggest that PGE deposition involved three stages. During the magmatic stage, sulfide melts were segregated at the base of the SIC and infiltrated the footwall rocks to form sulfide(-PGE) breccia and disseminated PGE mineralization (Crean Hill), and sulfide-PGE veins (Vermilion). Sulfide fractionation is suggested by the disappearance of Ru-bearing michenerite, a decrease in Ru, Rh and Ir tenors, and an increase in Pt, Pd and Au tenors and Cu/Ni away from the SIC contact. The syn-tectonic remobilization stage occurred between ~ 480–550 °C, as suggested by the composition of shear-hosted gersdorffite. At Crean Hill, Pd and Au were decoupled from Pt and remobilized via fluids into the footwall rocks, resulting in Pd and Au enrichment as disseminated michenerite and argentian gold along shear zones. At Vermilion, higher fluid-rock ratios and metamorphic semi-metal melts caused extensive remobilization of Pt, Pd and Au, and deposition of complex telluride, antimonide and arsenide grains within shear zones. A late metasomatic stage at &lt; 300 °C (gersdorffite composition) is observed at Vermilion only, where it caused epidote-albite-quartz-calcite alteration of the SIC rocks and deposition of low-temperature sulfides and precious metals in veins crosscutting shear zones. Together, these findings demonstrate how PGE mineralization should be examined relative to its host rock geology and evolution to resolve the distribution of precious metals in modified Ni-Cu-PGE deposits.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"25 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141836783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unraveling the evolution of the Bodó W-skarn district in the Seridó Mineral Province (NE-Brazil): constraints from C-O stable isotopes, thermodynamic modeling, and geochronology","authors":"Dinarte Lucas, Maria Helena B. M. Hollanda, João Adauto de Souza Neto, Renato Moraes, Laécio Cunha de Souza","doi":"10.1007/s00126-024-01300-4","DOIUrl":"https://doi.org/10.1007/s00126-024-01300-4","url":null,"abstract":"<p>Tungsten mineralization in the Bodó mineral district (9 Mt with an average grade of 2% WO₃) is in a sequence of metasomatized marbles and W-(Mo)-skarn lenses in the Seridó Belt, northern Borborema Province. The marble lenses have variable amounts of diopside, grossular, scapolite, phlogopite, and tremolite. The skarn lenses are mainly composed of massive grossular, diopside, vesuvianite, epidote, and quartz. A spatially related granite yielded a SHRIMP U‒Pb zircon date of 536.6 ± 3.4 Ma and a ⁴⁰Ar/³⁹Ar biotite date of 490.65 ± 0.67 Ma, whereas a nearby pegmatite yielded a ⁴⁰Ar/³⁹Ar muscovite date of 501.63 ± 0.59 Ma. Literature data for molybdenite in the skarn mineralization yielded a Re‒Os date of 510 ± 2 Ma, which is coeval with U‒Pb dates of columbite-tantalite from other regional pegmatites (515–509 Ma). Therefore, it is likely that pegmatite magmatism acted as the source of fluid and heat for the mineralization. The C–O stable isotope data for marbles and skarns are consistent with interaction of magmatic fluid and host marble at variable XCO₂ conditions. T-XCO₂ pseudosections define peak conditions of metamorphism/metasomatism at 650–600 °C over a wide range of XCO₂ (between 0.4 and 0.8), whereas the retrograde stage started at ~ 550 °C. Late garnet crystallization at low XCO₂ (&lt; 0.2) indicates high H₂O influx, while scapolite crystallization required high XCO₂ (~ 0.8). Together with the interpretation of textural relationships, these observations indicate that skarn and marble formation occurred under open-system conditions with fluctuating XCO₂ fluid composition as a consequence of magmatic fluid infiltration.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"16 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141768574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrological, geochemical and mineralogical characteristics of Wigu Hill carbonatite, Uluguru Mountains, Tanzania: insights into carbonatite evolution and REE mineralization","authors":"Mary Charles Moshi, Yasushi Watanabe, Nelson Boniface, Tatsuki Tsujimori, Carmela Tupaz, Daisuke Araoka, Shogo Aoki, Elisante E. Mshiu","doi":"10.1007/s00126-024-01295-y","DOIUrl":"https://doi.org/10.1007/s00126-024-01295-y","url":null,"abstract":"<p>The Wigu Hill Carbonatite, located south of Uluguru Mountain, is amongst the REE-endowed carbonatites in Tanzania. The carbonatite comprises apatite dolomite carbonatite that has been locally brecciated and intruded by small bodies of mica dolomite carbonatite. These early carbonatites are fine to medium grained, poorly enriched in REE₂O₃ (&lt; 0.4 wt%), and show elevated Nb (&gt; 200 ppm). The early carbonatites are crosscut by REE-bearing carbonatite dikes that host pegmatitic, well-preserved pseudomorphs after burbankite. The REE-bearing carbonatites are characterised by high REE₂O₃ (6–10 wt%), and pseudomorphs that vary in colour and mineralogy, reflecting the dissolution of primary burbankite through reaction with evolving carbothermal fluids in two major phases; (1) early altered burbankite formed yellow-colored pseudomorphs typified by an assemblage of synchysite-(Ce) with high (La/Ce)_N - (La/Nd)_N ratios, barite, Ca-strontianite, calcite, and quartz; and (2) subsequent late alterations by highly evolved fluids resulted into green and pink-colored pseudomorphs consisting of synchysite-(Ce) with low (La/Ce)_N - (La/Nd)_N ratios, barite, Ca-strontianite, fluorite, calcite, quartz, apatite, monazite, and Al-REE-phosphates. The stable C-O and Mg isotopes signatures of dolomite across Wigu Hill indicate a pristine mantle source (δ¹³C_VPDB -4.1‰ to -6.2‰; δ¹⁸O_VSMOW +6.5‰ to + 7.31‰ and δ²⁶Mg -0.44 to + 0.19‰), and are locally modified by surface processes which resulted in bastnaesite enriched zones with up to 15 wt% REE₂O₃. Textural, geochemical, and stable isotope data tracks a polygenetic evolution of Wigu Hill with the main REE mineralization phase occurring at the end of magmatic phase as a result of magmatic fractionations. Reworking by carbothermal fluids and locally by surface process has resulted in REE enrichment.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"88 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141768573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}